Foamed concrete is usually made by introducing a water-based, gas-filled foam into a paste that is typically formed with water and portland cement alone or portland cement with a fine, lightweight aggregate. The foamed paste hardens to form a low-density concrete that is used in either flooring or roofing applications where either thermal insulation or acoustical damping is required. Previously, portland cement was the preferred material used to produce foamed concrete. The foam structure was developed by adding gas-generating chemical to the portland cement paste or by mixing a preformed, water-based foam into the cement paste. Portland cement-based, foamed concretes are typically slow to cure and have relatively low strength. Reactive glass-based binder foams generally cure faster and have greater strength.
Foamed concretes are typically made using any of three well-known methods. The method using preformed foam requires that portland cement be mixed with a preformed aqueous foam that is produced using a commercial foaming agent. The usual foaming agents are hydrolyzed proteins. This approach requires a foam generator be on location to make the foam. Limitations of this technique are: i) the densities of a final foamed concrete produced is often non-uniform since the foam density used is not always the same; and ii) the foam begins to collapse from the moment it is formed since the foam is not self-generating.
A second method uses chemicals that are mixed with the portland cement to generate gas in the mixture. One of the most useful of these systems involves mixing hydrogen peroxide and calcium hypochlorite with cement and adding a foaming agent. The hydrogen peroxide and the calcium hypochlorite react to release oxygen and form calcium chloride solution. The limitations of this technique and cementious composition is the presence of chloride ions inherent in such a process which is unacceptable where steel reinforcement is used in the cement-based structure. Examples of this technique include U.S. Pat. No. 2,024,791 entitled "Process for the Manufacture of Masses and Articles Having A Porous Cellular Structure."
Also, this U.S. Pat. No. 2,024,791 discusses the use of powdered aluminum in a prior cement paste that will react with a lime-based cement that will release in the hydration process hydrogen gas that foams the cement paste. This aluminum-based foaming agent has an inherent limitation of being used in a non-uniform mixture where lack of uniform density may result and requires use of a portland-based cement that requires several days for curing. Hydrogen gas produced in the reaction may form an explosive mixture in air.
U.S. Pat. No. 3,095,312 entitled "Porous Foamed Silicate Products," teaches of using a comparable hydrogen peroxide or alkali metal peroxide gas foaming technique using water soluble inorganic metal silicates as the cementious based material along with a foaming additive of paraformaldehyde. Paraformaldehyde is a potential carcinogen that is harmful to humans and which is not desirable in construction areas.
U.S. Pat. No. 4,659,385 entitled "Building Material Manufacturing from Fly Ash" teaches of a comparable hydrogen peroxide gas foaming technique using fly ash with a water-miscible bonding agent that is preferably a polyvinyl acetate resin and an air entrainer.
A third method of production is the excess water system in which a water absorber, such as ground shale or diatomaceous earth, is used to retain water in the mixture, and the excess water is driven off during autoclave curing. This approach requires autoclave processing and cannot be adapted for onsite placement of the foamed concrete.
To overcome the limitations discussed above, the instant invention herein teaches of cementious-based composition that solves these problems while using inexpensive materials without the use of portland cements in the production thereof.